The disclosed invention is generally directed to ink jet printing, and more particularly to techniques for accurately detecting the top edge and/or bottom edge of print media for full bleed printing.
An ink jet printer forms a printed image by printing a pattern of individual dots at particular locations of an array defined for the printing medium. The locations are conveniently visualized as being small dots in a rectilinear array. The locations are sometimes called xe2x80x9cdot locations,xe2x80x9d xe2x80x9cdot positions,xe2x80x9d or xe2x80x9cpixelsxe2x80x9d. Thus, the printing operation can be viewed as the filling of a pattern of dot locations with dots of ink.
Ink jet printers print dots by ejecting very small drops of ink onto the print medium, and typically include a movable carriage that supports one or more printheads each having ink ejecting nozzles. The carriage traverses over the surface of the print medium, and the nozzles are controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to the pattern of pixels of the image being printed.
It has become desirable to provide xe2x80x9cedge to edgexe2x80x9d or xe2x80x9cfull bleed printingxe2x80x9d wherein the printed image extends to the edges of the print media, for example for photographic images.
A consideration with full bleed printing is the need to accurately determine the location of the leading and trailing edges (also referred to as top and bottom edges) of the print medium to avoid depositing excessive amounts of ink off the leading edge and trailing edge of the print media onto the media handling mechanism of the printer. Such off-media ink deposition causes unwanted marking of the back side of print media subsequently printed, which is deleterious to double sided printing. Also, the off-media deposition of ink could cause the media advance mechanism to malfunction.
The disclosed invention is directed to a printing apparatus that employs a media detect switch and a linear array optical detector to position an edge of a print medium that is generally transverse to the media axis in the field of view of the linear array which can have a field of view along the media axis that is less than the incremental media advances employed by the printing apparatus. In accordance with further aspects of the invention, such transversely extending edge of the print medium is scanned with the linear array to detect the location of the edge along the media axis, and printing is controlled so as to avoid printing off the print medium beyond the detected edge.